A large number of electronic devices, such as cordless telephones, computers, baby monitors, radios, and answering machines, which are found in the home and office do not possess a backup power supply. As a result, when power service is interrupted, these electronic devices are inoperable. For example, without power, cordless phones will not work, so in an emergency an individual can not make a call. To date, there is no cost effective means for consumers to provide an external backup power supply for their existing electronic devices that are powered by AC adapters.
Even if such an external backup power supply system existed, there is no means for consumers of average technical competence to correctly set the polarity for a backup power supply to match the incoming power. If the polarity of the backup power from a backup power supply is incorrectly set, the electronic device may be damaged.
Some prior electronic devices have tried to solve these problems by incorporating internal backup power supplies. In these electronic devices, the backup power supplies provide backup power when there is a power outage and the manufacturers of these devices make sure that the polarity of the backup power supplies matches the polarity of the incoming power. Although these internal backup power supplies work, these features add to the overall cost of the electronic devices. Even though backup power supplies are desirable for many electronic devices, some consumers do not want to pay for this additional feature for every electronic device they purchase.